Method of preventing of systemic-to-pulmonary-artery shunt thrombosis

ABSTRACT

The present invention is directed to the use of cangrelor for the treatment and/or prevention of shunt thrombosis in patients suffering congenital heart diseases undergoing shunt surgery. The invention is also directed to the use of cangrelor for the treatment and/or prevention of stent thrombosis in pediatric patients undergoing stent implantation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Ser. No. 62/524,102, filed onJun. 23, 2017, the entire contents of which are hereby incorporated byreference in their entirety.

FIELD OF THE INVENTION

The invention pertains to the field of thromboprophylaxis andparticularly to preventing stent thrombosis in pediatric patients,including neonates, and preventing shunt thrombosis in high riskpatients undergoing systemic-to-pulmonary artery shunt surgery. Neonateswith cyanotic congenital heart disease palliated with asystemic-to-pulmonary artery shunt are at high risk of thrombosis.

BACKGROUND OF THE INVENTION

Congenital heart defects (CHD) are the most common type of birth defect.It affects 8 out of every 1,000 newborns and has a wide range of diseaseseverity. However, the majority of those born with structural heartanomalies are otherwise healthy, and corrective procedures may result ina normal lifespan (Monagle, 2005). While great technical advances havebeen achieved in palliative and corrective measures and in the care ofcritically ill neonates, these procedures are associated with anincreased risk of acute thrombotic events (ATE) in this patientpopulation (Monagle, 2004; Tormene et al., 2006; Monagle et al., 2008;Manlhiot et al., 2011).

Palliation with a modified BT shunt is indispensable for the managementof a select group of neonates with cyanotic congenital heart disease.However, such patients are at high risk for thrombotic complicationssuch as acute shunt occlusion, which remains a major source of morbidityand mortality. Although aspirin therapy, in general, is thought toreduce the risk of shunt occlusion and improve survival, it is typicallynot administered until 12 to 24 hours after surgery. A limitedretrospective review of pediatric cardiac patients with evidence ofshunt occlusion at Columbia University Medical Center revealed that themajority of cases occurred prior to the administration of anantiplatelet agent, establishing an unmet need for thromboprophylaxisduring this vulnerable period.

Acute thromboembolic events (ATE) are rapidly becoming the new epidemicin centers that care for critically ill neonates due to an increase ininvasive monitoring, lifesaving technologies such as extracorporealmembrane oxygenation (ECMO), and new surgical techniques and graftmaterials used to repair complex congenital heart disease. (Monagle P,Newall F, Barnes C, Savoia H, Campbell J, Wallace T, Crock C. “Arterialthromboembolic disease: a single-centre case series study.” J PaediatrChild Health. 2008; 44:2832; Tormene D, Gavasso S, Rossetto V, SimioniP. “Thrombosis and thrombophilia in children: a systematic review.”Semin Throm. Hemost. 2006; 32:724-728; Manlhiot C, Menjak I B, Brandäo LR, Gruenwald C E, Schwartz S M, Sivarajan V B, Yoon H, Maratta R, CarewC L, McMullen J A, Clarizia N A, Holtby H M, Williams S, Caldarone C A,Van Arsdell G S, Chan A K, McCrindle B W. “Risk, clinical features, andoutcomes of thrombosis associated with pediatric cardiac surgery.”Circulation. 2011; 124:1511-1519; Chalmers E A. “Pediatric thrombosis.”J Clin Pathol. 2000; 53:419-423.) In the latter case, infants (<6months) constitute the major proportion (˜70%) of patients seen intertiary care centers with ATEs. (Monagle P. “Anticoagulation in theyoung.” Heart. 2004; 90:808-812.) In particular, those with singleventricle physiology who require a systemic-to-pulmonary artery shuntplacement (e.g. modified Blalock-Taussing or central shunts) are atgreatest risk, especially in the early postoperative period. (ManlhiotC, Menjak I B, Brandão L R, Gruenwald C E, Schwartz S M, Sivarajan V B,Yoon H, Maratta R, Carew C L, McMullen J A, Clarizia N A, Holtby H M,Williams S, Caldarone C A, Van Arsdell G S, Chan A K, McCrindle B W.“Risk, clinical features, and outcomes of thrombosis associated withpediatric cardiac surgery.” Circulation. 2011; 124:1511-1519; Fenton KN, Siewers R D, Rebovich B, Pigula F A. “Interim mortality in infantswith systemic-to pulmonary artery shunts.” Ann Thorac Surg. 2003;76:152-156; Monagle Paul. “Thrombosis in children with BT shunts,”Glenns and Fontans. Prog Pediatr Cardiol. 2005; 21:17-21; Al Jubair K A,Al Fagih M R, Al Jarallah A S, Al Yousef S, Ali Khan M A, Ashmeg A, AlFaraidi Y, Sawyer W. “Results of 546 Blalock-Taussig shunts performed in478 patients.” Cardiol Young. 1998; 8:486-490.) Consequently, this hasresulted in suboptimal postoperative outcomes as exemplified in aretrospective review of 2,058 neonates who underwent palliation with asystemic-to-pulmonary artery shunt at multiple centers; dischargemortality and complication rates were around an aggregate of 6.7% and12.3%, respectively. (Heidari-Bateni G, Norouzi S, Hall M, Brar A,Eghtesady P. “Defining the best practice patterns for the pediatricsystemic-to-pulmonary artery shunt procedure.” J Thorac Cardiovasc Surg.2014; 147:869-873.) Early institution of aspirin, an irreversibleinhibitor of platelet cyclooxygenase, within 12 hours of surgery hasreduced the risk of shunt thrombosis and death in this patientpopulation. (Al Jubair K A, Al Fagih M R, Al Jarallah A S, Al Yousef S,Ali Khan M A, Ashmeg A, Al Faraidi Y, Sawyer W. Results of 546“Blalock-Taussig shunts performed in 478 patients.” Cardiol Young. 1998;8:486-490; Heidari-Bateni G, Norouzi S, Hall M, Brar A, Eghtesady P.“Defining the best practice patterns for the pediatricsystemic-to-pulmonary artery shunt procedure.” J Thorac Cardiovasc Surg.2014; 147:869-873; Li J S, Yow E, Berezny K Y, Rhodes J F, Bokesch P M,Charpie J R, Forbus G A, Mahony L, Boshkov L, Lambert V, Bonnet D,Michel-Behnke I, Graham T P, Takahashi M, Jaggers J, Califf R M, RakhitA, Fontecave S, Sanders S P. “Clinical outcomes of palliative surgeryincluding a systemic-to-pulmonary artery shunt in infants with cyanoticcongenital heart disease: docs aspirin make a difference?” Circulation.2007; 116:293-297; Motz R, Wessel A, Ruschcwski W, Bürsch J. “Reducedfrequency of occlusion of aorto-pulmonary shunts in infants receivingaspirin.” Cardiol Young. 1999; 9:474-477). However, there remains anurgent need for pharmacologic protection prior to the administration ofan oral antiplatelet agent in order to minimize the period during whichpatients are vulnerable to an ATE.

Thienopyridines (e.g. clopidogrel) are a class of antiplatelet agentsthat target the ADP receptor P2Y12 and are known to reduce the risk ofischemia and thrombosis in adult patients during and after percutaneouscoronary intervention (PCI). They do so by impairing P2Y12 potentiationof platelet dense granule secretion in response to strong agonists,stabilization of platelet aggregates by contributing to the activationof αIIbβ3, and inhibition of the antiplatelet effects of prostacyclin.Despite its proven clinical efficacy, clopidogrel has several majordrawbacks that would limit it use during the vulnerable period forpost-operative pediatric cardiac patients. These include the requirementfor oral administration that may result in erratic absorptionparticularly in bypass cases, delay in the onset of action due to theneed for conversion of the pro-drug to an active metabolite, andirreversible inhibition of P2Y₁₂ that would necessitate platelettransfusion(s) if bleeding occurred

Interestingly, a previous clinical trial evaluating clopidogrel therapyin infants with cyanotic congenital heart disease palliated with asystemic-to-pulmonary-artery shunt failed to show any benefit inreducing the rate of death or shunt-related morbidity in drug treatedpatients. In the majority of cases, patients were also receiving aspirintherapy at the time of administration of clopidrogrel. Of note,clopidrogrel is a prodrug that requires metabolism by the liver togenerate its active form, which was unknown at the time that study wasperformed. It is also an irreversible inhibitor of the P2Y12 receptor.Target value for platelet inhibition in that trial was ˜30% asdetermined by LTA. One major conclusion drawn from this study was thatplatelets from these young patients might be less responsive to agonistssuch as ADP as evidenced by the lower dose of clopidogrel needed toachieve similar levels of inhibition of platelet aggregation using LTAas compared to adults. This suggested that the P2Y12 signaling pathwaymay be developmentally regulated and/or of less importance in supportingthrombus generation in this population as compared to adults.

Cangrelor, an adenosine triphosphate (ATP) analogue, is a P2Y12 receptorantagonist given intravenously with properties more suitable forshort-term use, which include a rapid, direct, predictable, andreversible inhibition of platelet function. It does not requireconversion to an active form as compared to clopidogrel. It has ahalf-life of 3 to 6 minutes in adults with restoration of hemostasis, asassessed by bleeding time, seen within 10 minutes of cessation ofinfusion of a supratherapeutic dose and full platelet function recoverywithin 60 minutes as determined by response to ADP.

The alternatives forms and salts of cangrelor, processes for theirproduction, and pharmaceutical compositions comprising them, are wellknown in the art and set forth, for example, in U.S. Pat. No. 5,721,219.Additional disclosure relevant to the production and use of cangrelormay be found in U.S. Pat. Nos. 5,955,447; 6,130,208; 6,114,313;8,680,052; 759,316; 9,295,687; 9,427,448; 9,439,921; and 9,700,575.

Cangrelor is also rapidly inactivated by dephosphorylation to thenucleoside. On the basis of these characteristics, it was selected forclinical development as an IV antithrombotic agent and has recently beenapproved by the FDA for use in adults undergoing PCl.

Cangrelor may also have value as a potential bridging agent to oraltherapy in neonates with cyanotic congenital heart disease who requirepalliation with a systemic-to-pulmonary-artery shunt.

Despite advances in adjunctive pharmacotherapy, there remains an urgentneed for pharmacologic protection prior to the administration of an oralantiplatelet agent in order to minimize the period immediately aftersurgery during which patients, in particular the pediatric patients, arevulnerable to an acute thrombotic event (ATE).

We provide a pharmaceutical composition comprising a P2Y₁₂ inhibitor asanti-platelet agents for use in preventing and/or treating thrombosis,having pharmacological properties that are well suited for criticallyill pediatric and pediatric patients with congenital heart diseaserequiring thromboprophylaxis.

SUMMARY OF THE INVENTION

The present invention is directed to a use of cangrelor in the treatmentand/or prevention of shunt thrombosis in patients suffering congenitalheart disease. Additionally, the present invention is directed to theuse of cangrelor in the treatment and/or prevention of shunt or stentthrombosis in pediatric patients undergoing shunt surgery or stentimplantation respectively. Another aspect of the invention provides apharmaceutical composition comprising cangrelor for use in patientssuffering congenital heart disease undergoing shunt surgery.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in the treatment and/or prevention of shuntthrombosis in patients undergoing shunt surgery wherein the shuntsurgery is selected from the group including systemic-to-pulmonaryartery shunt, Blalock-Taussing shunt, central shunt, or right ventricleto pulmonary artery palliative shunts.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in patients undergoingsystemic-to-pulmonary artery shunt surgery.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in the treatment and/or prevention of shuntor stent thrombosis in pediatric patients suffering congenital heartdisease.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in the treatment and/or prevention of shuntor stent thrombosis in pediatric patients undergoing shunt surgery orstent implantation surgery.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in pediatric patients undergoing shuntsurgery or stent implantation wherein the shunt surgery or stentimplantation is selected from the group including systemic-to-pulmonaryartery shunt, Blalock-Taussing shunt, central shunt, right ventricle topulmonary artery palliative shunts, or ductus arterious stents.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in pediatric patients wherein the pediatricpatients suffer single ventricle physiology palliated withsystemic-to-pulmonary artery shunt.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in the treatment and/or prevention of shuntor stent thrombosis wherein the administration is intravenous. Thepatient population for shunt thrombosis prevention and/or treatment isadult and pediatric patients, including neonate. The patient populationfor stent thrombosis prevention and/or treatment is pediatric patients,including neonates.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in the treatment and/or prevention of shuntor stent thrombosis wherein the method comprises:

i) performing the shunt surgery or stent implantation;ii) administering the composition comprising cangrelor after surgery.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor wherein the composition is administered as a bolus,or as a continuous infusion, or as a bolus followed by a continuousinfusion, or as a continuous infusion followed by a bolus.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for the above indications, wherein the amount ofcangrelor administered as continuous infusion is between about 0.1 andabout 4 μg/kg/min. Preferably, the amount of cangrelor is between about0.1 and 1.5 μg/kg/min, more preferably between about 0.1 and 1μg/kg/min, even more preferably from about 0.1 and 0.5 μg/kg/min, wherestill more preferred amount is between about 0.1 and 0.3 μg/kg/min.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use as a bridging agent to oral antiplatelettherapies in pediatric patients undergoing shunt surgery or stentimplantation.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use as a bridging agent to oral antiplatelettherapies in pediatric patients undergoing shunt surgery or stentimplantation wherein the shunt surgery or stent implantation is selectedfrom the group including systemic-to-pulmonary artery shunt,Blalock-Taussing shunt, central shunt, right ventricle to pulmonaryartery palliative shunts or ductus arterious stents.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use as a bridging agent to oral antiplatelettherapies in pediatric patients undergoing shunt surgery or stentimplantation, wherein the administration comprises:

i) administering a continuous infusion of cangrelor after shunt surgeryor stent implantation for at least one hour or longer;ii) discontinuing the treatment with cangrelor;iii) administering the oral antiplatelet therapy.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use as a bridging agent wherein the continuousinfusion of cangrelor is preferably carried out at a dosage as abovedefined.

Another aspect of the invention provides a pharmaceutical compositioncomprising cangrelor for use in preventing acute stent thrombosis inpatients undergoing orthotopic heart transplant.

Another aspect of the invention provides a method of preventing shuntthrombosis in high risk pediatric patients undergoingsystemic-to-pulmonary artery shunt surgery.

Another aspect of the invention is a method of preventing shuntthrombosis in a high risk patient undergoing systemic-to-pulmonaryartery shunt surgery, the method comprising:

i) performing systemic-to-pulmonary artery shunt surgery andii) administering cangrelor immediately after surgery.

The high risk patient preferably is a pediatric patient, most preferablya neonate.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1. Time from surgery to shunt occlusion in pediatric cardiacpatients. The data represent postoperative in-hospital population from2013 to 2015. Dotted line denotes the time aspirin (ASA) is typicallygiven by enteral route.

FIG. 2. P2Y12 receptor expression and ADP response of platelets. Arepresentative flow cytometry histograms of antibody staining for theP2Y12 receptor on resting platelets isolated from pediatric cardiacpatients (NCP) versus healthy adults (n=5 independent experiments).Histograms of antibody staining for GPIbα (CD42b) and integrin αIIbβ3(CD61) are shown for comparison. B-E, Concentration response curves forthe determination of EC50 values for ADP as measured by lighttransmission aggregometry (LTA) using purified platelets from pediatricand pediatric patients with congenital heart disease or healthy adultvolunteers in the presence of fibrinogen. Results are the mean ±SEM;n=4-6 individuals for each concentration of ADP tested.

FIG. 3. Effect of cangrelor on platelet aggregation in response to ADP.A-D, Representative tracings of ADP (20 μM)-induced aggregation ofplatelets isolated from pediatric and pediatric patients with congenitalheart disease or healthy adult volunteers in the presence of indicatedconcentrations of cangrelor.

FIG. 4. IC50 curves for cangrelor using LTA and a microfluidic device.Concentration response curves for the determination of IC50 values for20 μM ADP (A-D) and 5 μM ADP (E-H) as measured by LTA using purifiedplatelets from pediatric and pediatric patients with congenital heartdisease or healthy adult volunteers in the presence of fibrinogen. Datarepresent the mean ±SEM. n=4-6 individuals for each concentration ofantagonist tested. I-J, Concentration response curves for cangrelorunder flow conditions. A microfluidic device containing a thrombogenicsurface of collagen was used to determine IC50 values for cangreloradded to PPACK-treated whole blood from pediatric patients with singleventricle physiology (n=4; 38 separate clotting events) or healthyadults (n=7; 56 separate clotting events). Data represent the mean ±SEM.

FIG. 5. Human platelet interactions with plasma VWF in flow. A,Accumulation of human platelets on surface-immobilized VWF obtained frommice possessing the human A1 domain (VWFHA1). Whole blood from pediatricpatients with single ventricle physiology or healthy adults was infusedover the reactive substrate for 3 min (wall shear rate of 1,600 s−1)before assessing the number of interacting platelets. mAb 6D1 is afunction blocking antibody to VWF receptor on platelets GPIbα. C, Theability human platelets translocating on surface-immobilized mouseplasma VWFHA1 to undergo firm adhesion and arrest in response to ADPstimulation. Abciximab is a function blocking antibody to integrinαIlbβ3, which is required for firm adhesion. Data represent the mean±SEM (n=5 individuals per group).

FIG. 6. Effect of cangrelor on human platelet thrombus formation inavatar mice. Time course of the average size of thrombi formed (A-D) andmaximal thrombus size obtained (E) in laser-injured arterioles of VWFHA1mutant mice pre- and post-administration of cangrelor (same animal). Theeffects of the αIIbβ3 inhibitor abciximab (0.25 μg/kg bolus; 0.125μg/kg/min infusion) are shown for comparison (n=3 independentexperiments for each age group). Each symbol (E) represents the area ofa thrombus in 1 arteriole of a mouse. Results for cangrelor are the mean±SEM of 8 independent experiments performed for each age group ofpediatric patients with CHD or healthy adult volunteers. F, Percentchange in thrombus size in response to cangrelor treatment based on datashown in E. Data are from represent mean ±SEM.

FIG. 7. Pharmacodynamic properties of cangrelor administered to neonateswith CHD in the early post-operative period. A phase 1 clinical trial iscurrently being conducted to assess the drug plasma levels and effectson platelet aggregation using LTA and microfluidics. A, representativeLTA results from a post-operative neonate with shunt placement 1 h priorto receiving cangrelor, 15 minutes prior to the end of the infusion (0.5microgram/kg/min for 1 h), and 1 h after stopping the infusion ofcangrelor. B, microfluidic results under the same conditions as outlinedfor LTA. Results are compared to a healthy adult who did not receivecangrelor.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to use of cangrelor for preventingand/or treating shunt thrombosis in a patient suffering congenital heartdisease. In one embodiment, the patients are pediatric patients havingcyanotic heart diseases.

The invention is thus directed to the use of cangrelor for preventingand/or treating shunt or stent thrombosis in a high-risk patientundergoing surgery for placement of palliative shunts or implantation ofa stent. Typically, the surgery includes the placement of systemic topulmonary shunts, Blalock-Taussing shunt, central shunts, rightventricle to pulmonary artery palliative shunts or ductus artcriousstents. Advantageously according to the method of the present invention,the cangrelor is administered after surgery according to the abovepreferred embodiments, thus reducing the risk of acute thromboembolicevents, particularly in pediatric patients.

As before reported, the patients undergoing the above mentioned shuntsurgery or stent implantation, are at a high risk for thromboticcomplications such as, without limitation, acute shunt occlusion, whichremains a major source of morbidity and mortality.

It has to be noted that the well known and widely used aspirin therapymay help in reducing the risk of shunt occlusion, but it is typicallynot administered until 12 to 24 hours after surgery; therefore there isa vulnerable period immediately after surgery or implantation up to theadministration of aspirin wherein the risk of onset of acutethromboembolic events is not managed. To date, there are no otherantiplatelet therapies available that possess the desiredcharacteristics of cangrelor, which include i.v. administration, rapidonset, rapid reversibility, and a form that does not require metabolictransformation for blockade of the P2Y12 receptor. These characteristicsare ideal for this patient population that are both high risk for clotformation and bleeding in the early post-operative period.

The method of the present invention provides an efficacious method oftreatment and/or prevention of thrombotic complications, particularly inpediatric patients, said method comprising the administration ofcangrelor, shortly after the termination of the surgery, and in anotherembodiment, also in combination with an oral antiplatelet therapy.According to the invention, cangrelor is preferably administeredintravenous by continuous infusion at a dosage, as above detailed, whichis well suited, tolerated and safe also for pediatric patients.

In particular, the invention is directed to the use of cangrelor forprevention and/or treatment of shunt thrombosis in a high risk pediatricpatients have single ventricle physiology undergoingsystemic-to-pulmonary artery shunt surgery.

DEFINITIONS

In each aspect of the present invention, the term “cangrelor”encompasses the compound of Formula 1, as well as tautomeric,enantiomeric and diastercomeric forms thereof, and raccmic mixturesthereof, and pharmaceutically acceptable salts of these compounds,including a tetrasodium salt.

In the present application, unless otherwise provided, the definition ofpediatric patients includes individuals from birth to about 18 years, ora length-based weight (per Broselow Tape) of 36 kg or less. Patients whoare known to be less than about 18 years of age but whose weight exceeds36 kg may still be considered pediatric patients given theirchronological age; however weights will then need to be estimated andadult dosages should be used. Thus, the pediatric patients includese.g.: newborns up to about the first 28 days of life; newborns up toabout 12 months; pediatric patients from: up to about 18 years; about 1to about 3 years, from about 3 to about 5 years, from about 6 to about10 years, from about 11 to about 14 years, and from about 14 to about 18years.

Congenital heart defects (CHD) or congenital heart disease (CHD) arestructural problems arising from abnormal formation of the heart ormajor blood vessels. At least 18 distinct types of congenital heartdefects are recognized, with many additional anatomic variations. Theword “congenital” means existing at birth. Congenital heart defects maybe cyanotic or acyanotic.

Examples of common type of congenital heart disease are, but are notlimited to: Aortic Valve Stenosis (AVS), Atrial Septal Defect (ASD),Coarctation of the Aorta (CoA), Complete Atrioventricular Canal defect(CAVC), d-Transposition of the Great Arteries, Ebstein's Anomaly,Hypoplastic Left Heart Syndrome, I-Transposition of the Great Arteries,Patent Ductus Arteriosus (PDA), Pulmonary Atresia, Pulmonary ValveStenosis, Single Ventricle Defects, Tetralogy of Fallot, Total AnomalousPulmonary Venous Connection (TAPVC), Tricuspid Atresia, TruncusArteriosus, and Ventricular Septal Defect (VSD).

In the present description, unless otherwise provided, the definition ofshunt surgery includes, but is not limited to: systemic-to-pulmonaryartery shunts, Blalock-Taussing shunts, central shunts, or rightventricle to pulmonary artery palliative shunts.

In the present description, unless otherwise provided, the definition ofstent implantation or stent surgery includes, but is not limited toductus arterious stents.

DETAILED DESCRIPTION

In one aspect, the present invention demonstrates by means of standardLTA, high throughput microfluidic devices, and novel biologicalplatforms that cangrelor is effective in preventing and treatingthrombus formation in high risk pediatric populations suffering fromcongenital heart disease.

Platelet response to ADP and cangrelor was nearly identical for all agegroups tested (P>0.05) based on calculated EC50 and IC50 values obtainedby LTA.

The in vitro potency of cangrelor was further evaluated using wholeblood from pediatric patients with single ventricle physiology and highthroughput micro fluidic assays, which yielded similar IC50 values.Consistent with these findings was the observation that platelets frompediatric patients expressed similar levels of the P2Y12 receptor astheir adult counterparts.

To demonstrate the therapeutic utility of cangrelor in a biologicallyrelevant model of thrombosis, we also evaluated the in vivo behavior ofplatelets from neonates and older patients with congenital heart diseasein laser-injured arterioles of avatar mice (mice that have beengenetically modified to support human platelet mediated hemostasis andthrombosis) before and immediately after drug administration. In allcases, cangrelor given at doses recommended for percutaneous coronaryintervention (per 1 kg of body weight) reduced thrombus size by >45%thereby preventing vessel occlusion (P<0.0001).

To demonstrate the potential clinical utility of cangrelor, we firstassessed the reactivity of platelets from neonates with cyanoticcongenital heart disease, and in particular the contribution of theP2Y₁₂ receptor in supporting aggregation and thrombus formation.

By using standard as well as novel in vitro and in vivo basedtechnologies, there were no significant differences in platelet responseto either ADP-induced aggregation or cangrelor-mediated P2Y₁₂ receptorblockade for neonates and older pediatric patients with congenital heartdisease as compare to healthy adults. In fact, EC₅₀ and IC₅₀ values,respectively, were nearly identical as determined by LTA using purifiedplatelets.

As demonstrated in the present Experimental section, platelets frompediatric patients with cyanotic congenital heart disease have a nearlyidentical response to ADP and P2Y₁₂ receptor blockade as their adultcounterparts. Cangrelor may prove to be an effective antithrombotic drugwith pharmacological properties well suited for use in the immediatepost-operative period for neonates palliated with asystemic-to-pulmonary artery shunts.

Although ex-vivo technologies such as flow cytometry, aggregometry, andmicrofluidic devices can yield important information concerningpediatric platelet function and drug response, they cannot fullyreplicate the complex adhesion and activation events critical forthrombus formation on the arterial side of the circulation. To addressthis issue, we utilized an avatar mouse model that better reflects theintravascular environment in humans by permitting human but not mouseplatelets to support biologically relevant interactions at sites ofvascular injury.

In fact, the power of this biological platform in assessing theantithrombotic properties of P2Y₁₂ inhibitors such as the thienopyridinederivative clopidogrel, was accomplished by evaluating the ability ofplatelets isolated from drug treated adults to support thrombusformation in laser-injured arterioles of these animals. Consistent withthis dependency on the P2Y₁₂ receptor for maximal thrombus generationwas the ability of cangrelor to limit the ability of platelets fromneonates and older pediatric patients with congenital heart disease tosupport clot growth and vessel occlusion. Advantageously, cangrelor didnot completely prevent platelet accumulation at sites of arterioleinjury as compared to integrin αIIbβ3 inhibitor abciximab, which nearlyabrogated platelet-vessel wall interactions.

A previous clinical trial evaluating the P2Y₁₂ inhibitor clopidogrel ininfants with cyanotic congenital heart disease palliated with asystemic-to-pulmonary artery shunt failed to demonstrate any significantreduction in either mortality from any cause or shunt-related morbidity.

In addition to the prevention of shunt thrombosis, there may be otherindications for the use of cangrelor in this high risk population.Despite an overall improvement in survival after a multistage palliativerepair for hypoplastic left heart syndrome, patients may ultimatelyrequire an orthotopic heart transplant. However, it has been reportedthat as many as 25% of transplant patients will develop cardiacallograft vasculopathy necessitating coronary artery revascularizationand stent placement as a short-term palliative solution. In fact, arecent study has suggested that PCI can be performed safely andeffectively in this patient population, and has value as part of anevolving strategy to improve outcomes prior to re-transplantation.Cangrelor, which has been shown to significantly reduce ischemic eventsduring PCI in adults with coronary artery disease without significantlyincreasing the risk of severe bleeding, may play a role in preventingacute stent thrombosis in these patients as well.

In one embodiment, the present invention is directed to the use ofcangrelor for the treatment and/or prevention of acute stent thrombosisin pediatric patients undergoing or who have undergone orthotopic hearttransplant. These patients typically need coronary arteryrevascularization and stent placement as a short-term palliativesolution.

Given that shunt thrombosis remains a major cause of morbidity andmortality and that patients are at highest risk during the initiallypalliation for single ventricle physiology, we herein surprisinglypresent preclinical evidence that the non-thienopyridine P2Y₁₂ inhibitorcangrelor may fill a critical therapeutic void in thromboprophylaxis.This is justified based on the results reported in the presentinvention, demonstrating that platelets from pediatric patients withcyanotic congenital heart disease have a robust response to ADP and aresurprisingly as amenable to P2Y₁₂ inhibition with cangrelor as theiradult counterparts. Moreover, these findings are not restricted topediatric shunt patients but appear to be independent of age and type ofcardiac lesion.

Unique to this study is the ability to establish the in vivo efficacy ofcangrelor using an avatar mouse model that permits the evaluation ofhuman platelet interactions with the injured vessel wall, thusdemonstrating that this P2Y₁₂ inhibitor yields the intended biologicalresponse.

In addition, in vitro data obtained from a phase 1 PK/PD clinical trialinvolving the infusion of cangrelor at 0.5 μg/kg/min or 0.25 μg/kg/minfor one hour in post-operative neonates with CHD that requiredpalliation with a systemic to pulmonary artery shunt demonstrated boththe efficacy and rapid reversibility o f cangrelor as assessed by LTAand microfluidics (FIG. 7).

The above nonclinical and clinical studies provide compelling evidencefor an efficacious use of cangrelor in the prevention and/or treatmentof shunt or stent thrombosis in patients suffering congenital heartdisease who require palliation with a systemic to pulmonary arteryshunt.

It is understood that all preferred groups or embodiments of the presentinvention described above may be combined with each other and apply aswell mutatis mutandis.

In one aspect, the invention provides the use of cangrelor in theprevention and/or treatment of shunt thrombosis in patients sufferingcongenital heart disease undergoing shunt surgery. The treatment and/orprevention of shunt thrombosis in high risk patients undergoing shuntsurgery comprises performing shunt surgery and administering cangrelorimmediately after surgery.

In another aspect, the invention provides the use of cangrelor for theprevention and/or treatment of shunt or stent thrombosis in pediatricpatients with cyanotic congenital heart disease palliated with asystemic-to-pulmonary artery shunt, Blalock-Taussing shunt, centralshunt, right ventricle to pulmonary artery palliative shunts, and ductusarterious stents, wherein the pediatric patients are at high risk forthrombotic complications. The thrombotic complications or acutethromboembolic events such as acute shunt occlusion remain a majorsource of morbidity and mortality.

In a preferred embodiment, the invention provides the use of cangrelorfor prevention and/or treatment of shunt thrombosis in a high riskpediatric patients undergoing systemic-to-pulmonary artery shuntsurgery. The pediatric patients have single ventricle physiology.

In another aspect, the invention provides the use of cangrelor forprevention and/or treatment of stent thrombosis in a high risk pediatricpatients palliated with a ductus arterious stents.

In another aspect, the invention provides the use of cangrelor to reducethe incidence and/or prevent the mortality in high-risk patientsundergoing a shunt surgery, wherein mortality may be associated withacute thrombotic events. The high-risk patients are pediatric patientswith congenital heart disease. In particular, the pediatric patientshave single ventricle physiology.

In another aspect, the invention provides the use of cangrelor to reducethe incidence and/or prevent the mortality in high-risk pediatricpatients undergoing a stent surgery, wherein mortality may be associatedwith acute thromboembolic events. The high-risk patients are pediatricpatients with congenital heart disease.

The invention also provides pharmaceutical composition comprisingcangrelor for the administration once or according to a dosing regimenwherein a number of doses are administered at varying intervals of timefor a given period of time.

Administration of pharmaceutical compositions comprising cangrelor maybe accomplished according to patient needs, for example oral,sublingual, intranasal, intraocular, rectal, transdermal, mucosal,topical or parenteral administration. Parenteral modes of administrationinclude without limitation, intradermal, subcutaneous (s.c., s.q.,sub-Q, Hypo), intramuscular (i.m.), intravenous (i.v.), intraperitoneal(i.p.), intra-arterial, intramedulary, intracardiac, intra-articular(joint), intrasynovial (joint fluid area), intracranial, intraspinal,and intrathecal (spinal fluids).

Any known device useful for parenteral injection or infusion of drugformulations can be used in the methods of the present invention.

In a preferred embodiment of the invention, the administration is viaparenteral, more preferably intravenous administration, via a peripheralIV or central venous line.

When administered intravenously, the pharmaceutical compositioncomprising cangrelor may be administered as a bolus, as a continuousinfusion, as a bolus followed by a continuous infusion, or as acontinuous infusion followed by a bolus.

In one embodiment the invention provides a pharmaceutical compositioncomprising cangrelor wherein the point in time when the pharmaceuticalcomposition is administered is between about a half an hour and about 24hours from the termination of the shunt surgery or stent implantation,such as at least about half an hour, about 1 hour, about 2 hours, about3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours,about 8 hours, about 9 hours, and about 10 hours or longer from thetermination of the shunt surgery or stent implantation. Preferably, theadministration is after at least about 1 hour, more preferably in aperiod of time comprised between about 2 and about 4 hours from thetermination of the shunt surgery or stent implantation.

Preferably, the pharmaceutical composition comprising cangrelor isadministered as continuous infusion. For example, the pharmaceuticalcomposition according to the invention may be administered after theshunt surgery or stent implantation as a continuous infusion for atleast about 10 minutes to about 72 hours. Preferably, the administrationcontinues for at least about 1 hour, about 2 hours, about 3 hours, about4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours,about 9 hours, or about 24 hours or longer. More preferably, theinfusion continues for at least about 10 minutes to about 2 hours; stillmore preferably, the infusion continues for at least one hour, or for ashort period of time such as less than about an hour, such as about 15minutes, about 30 minutes or about 45 minutes depending for example onthe dosage, the age or the weight of the patients.

When the pharmaceutical composition comprising cangrelor is administeredas a bolus,

it is administered within a short period of time, such as about twominutes or less, or about one minute or less, after shunt surgery orstent implantation.

In one aspect of the present invention, cangrelor can be administeredbefore, during, and/or after shunt surgery or stent implantation.

When administered as a bolus, cangrelor is administered at dosagebetween about 5 μg/kg and about 100 μg/kg, preferably between about 5μg/kg and about 40 μg/kg, even more preferably between about 10 μg/kgand about 35 μg/kg, still more preferably between about 10 μg/kg andabout 30 μg/kg. For example, the pharmaceutical composition comprisingcangrelor is administered at about 5 μg/kg, about 10 μg/kg, about 15μg/kg, about 20 μg/kg, about 25 μg/kg, or about 30 μg/kg.

In one embodiment, an intravenous dose of up to about 4microgram/kg/min, can be administered about 2 to about 4 h after shuntsurgery or stent implantation and continued until the preferred time ofadministration of an oral agent.

The composition may be administered once, twice, thrice or more times aday.

In a further embodiment, the pharmaceutical composition comprisingcangrelor is administered once the acute thromboembolic event isrecognized or diagnosed, or at the onset of symptoms of the acutethromboembolic event.

For example, the pharmaceutical composition may be administered whensymptoms of acute thromboembolic event are observed. The pharmaceuticalcomposition is administered within a short period of time from the onsetof symptoms of acute thromboembolic event.

The short period of time may range from about one or about two minutesto about one or about two hours.

In some embodiments, the method comprises administering thepharmaceutical composition comprising cangrelor as a prophylaxis againstan acute thromboembolic event.

Patients appropriate for such prevention include pediatric cardiacsubjects who are undergoing shunt surgery or stent implantation forplacement of systemic-to pulmonary artery palliative shunts (e.g.,Blalock-Taussig or central shunt), right ventricle to pulmonary arterypalliative shunts, or ductus arteriosus stents who are at risk ofthrombotic events after repair of structural congenital heart disease.

In another aspect, the present invention provides the administration ofpharmaceutical composition comprising cangrelor for the treatment ofshunt or stent thrombosis in pediatric patients undergoing stentimplantation or shunt surgery concurrently or sequentially (before orafter) with at least one additional therapeutic agent.

The additional therapeutic agent may be, for example without limitation,a P2Y12-receptor inhibitor such as an oral P2Y12-receptor inhibitor, aglycoprotein IIb/IIIa inhibitor, aspirin and heparin. Administering anoral antiplatelet therapies, either concurrently or sequentially withthe pharmaceutical composition comprising cangrelor in pediatricpatients undergoing shunt surgery or stent implantation may alsotransition the patient to chronic or maintenance treatment with theantiplatelet inhibitor.

As mentioned above, the present invention also provides the use ofcangrelor as a bridging agent to oral antiplatelet therapies inpediatric patients requiring a palliative systemic-to-pulmonary arteryshunt, Blalock-Taussing shunt, central shunt, right ventricle topulmonary artery palliative shunt or ductus arterious stent.

In one embodiment, the cangrelor is useful for transitioning pediatricpatients from administration of cangrelor after shunt surgery or stentimplantation to administration of a chronic or maintenance treatmentwith oral antiplatelet therapies, i.e. oral P2Y12, or aspirin.

In a preferred embodiment, the pharmaceutical composition comprisingcangrelor is administered in a method comprising:

i) administering a continuous infusion of cangrelor after shunt surgeryor stent implantation for at least half an hour to about 72 hours;

ii) discontinuing the treatment with cangrelor; and

iii) administering the oral antiplatelet therapy.

In a further embodiment, the use of cangrelor in a method fortransitioning pediatric patients from administration of cangrelor aftershunt surgery or stent implantation to administration of a chronic ormaintenance treatment with oral antiplatelet therapies includes acontinuous infusion of cangrelor after shunt surgery or stentimplantation at a dosage according to the above indicated preferredones.

Cangrelor can be administered alone or combined with variouspharmaceutically acceptable excipients.

The pharmaceutical composition of the present invention comprisescangrelor, and may further comprise one or more pharmaceuticallyacceptable excipients.

These pharmaceutical compositions may comprise one or morepharmaceutically acceptable excipients including, but not limited to,carriers, diluents, stabilizing agents, solubilizing agents,surfactants, buffers, antioxidants, preservatives, tonicity agents,bulking agents, lubricating agents, emulsifiers, suspcnding or viscosityagents, fillers, disintegrating agents, binding agents, wetting agents,lubricating agents, antibacterials, antibiotics, antifungals, chelatingagents, sweeteners, perfuming agents, flavoring agents, coloring agents,administration aids, and combinations thereof.

Particular excipients include, but are not limited to, cornstarch orgelatin, lactose, sucrose, dextrose, microcrystalline cellulose, kaolin,mannitol, sorbitol, dicalcium phosphate, sodium chloride, alginic acid,croscarmellose sodium, sodium starch glycolate, glycerol, ethanol,propylene glycol, polysorbate 80 (Tween-80™ ), poly(ethylene)glycol 300and 400 (PEG 300 and 400), PEGylated castor oil (e.g. Cremophor EL),poloxamer 407 and 188, cyclodextrin or cyclodextrin derivatives(including HPCD ((2-hydroxypropyl)-cyclodextrin) and (2hydroxyethyl)-cyclodextrin), hydrophilic and hydrophobic carriers, andcombinations thereof.

Hydrophobic carriers include, for example, fat emulsions, lipids,PEGylated phospholipids, polymer matrices, biocompatible polymers,lipospheres, vesicles, particles, and liposomes. In certain embodiments,the pharmaceutical compositions may comprise polyols, such as sorbitol,lactose, sucrose, inositol or trehalose.

The pharmaceutical compositions of the present invention may beformulated for the route by which they are administered to the patients,which include solids, liquids, and suspensions. For example, if thepharmaceutical composition is formulated for IV administration, thepharmaceutical composition may comprise an intravenous fluid, whichincludes, but is not limited to, water-for-injection (WFI),physiological saline, 0.9% NaCl, phosphate buffered saline, 5% dextrosein water, and 0.002% polysorbate 80 in water or Ringer's™ solution.

Such compositions may comprise cangrelor in an amount of about comprisedbetween 0.10 and 200 μg/mL.

If the pharmaceutical composition is formulated for intramuscularadministration, the pharmaceutical composition may comprise anintravenous fluid, which includes, but is not limited to, WFI,physiological saline, 0.9% NaCl, phosphate buffered saline, and 5%dextrose in water.

If the pharmaceutical composition is formulated for oral administration,the pharmaceutical composition may comprise excipients that include, butare not limited to diluents (e.g., sodium and calcium carbonate, sodiumand calcium phosphate, and lactose), binding agents (e.g., acacia gum,starch, gelatin, sucrose, polyvinylpyrrolidone (Povidone), sorbitol,tragacanth, methylcellulose, sodium carboxymethylcellulose,hydroxypropyl methylcellulose, and ethylcellulose), fillers (e.g.,calcium phosphate, glycine, lactose, maize-starch, sorbitol, orsucrose), wetting agents, lubricating agents (e.g., metallic stearates,stearic acid, polyethylene glycol, waxes, oils, silica and colloidalsilica, silicon fluid or tale), disintegrating agents (e.g., potatostarch, corn starch and alginic acid), flavouring agents (e.g.peppermint, oil of wintergreen, fruit flavoring, bubblegum, and thelike), and coloring agents.

Excipients may also include coatings such as glyceryl monostearate orglyceryl distearate, to delay absorption in the gastrointestinal tract.For oral use, the pharmaceutical composition may be made in the form ofa tablet, capsule, suspension or liquid syrup or elixir, wafers and thelike.

The pharmaceutical compositions of the present invention may be preparedby admixing cangrelor with the one or more pharmaceutically acceptableexcipients. Methods of admixing and devices useful for admixing areknown in the art.

In certain embodiments, cangrelor and the one or more pharmaceuticallyacceptable excipients are dissolved and then admixed. The resultingmixture may be dried, such as through lyophilization, to form a solidpharmaceutical composition, or the resulting mixture may remain insolution form as a liquid pharmaceutical composition. In someembodiments, the solid pharmaceutical composition may be solubilized inan intravenous fluid before administration, for example, as a bolus orinfusion.

In some embodiments, the pharmaceutical composition is prepared bydissolving and admixing cangrelor, mannitol, sorbitol, and optionallysodium hydroxide, and then lyophilizing the mixture. Prior toadministration, the lyophilized mixture is dissolved in an intravenousfluid such as WFI or physiological saline.

The following examples illustrate the invention, without any limitation.

EXPERIMENTAL PART Methods Reagents

ADP and type 1 collagen (ChronoPar) were obtained from Chronolog(Havertown, Pa.). Human fibrinogen was purchased from Sigma Co. (SaintLouis, Mo.) and abciximab (ReoPro) from Centocor, Inc (Marvin, Pa.). Thepolyclonal anti-VWF antibody and Alexa 488 conjugated antihuman CD61(GPIIIa) antibody were purchased from Dako (Carpinteria, Calif.) andBio-Rad (Raleigh, N.C.; clone Y2/51), respectively. MAb 6D1 (functionblocking antibody to human GPIbα) and cangrelor (P2Y12 inhibitor) werekindly provided by Barry Coller (Rockefeller University, N.Y.) and TheMedicine Company (Parsippany, N.J.).

Mice

VWF^(HA1) mutant animals were generated and backcrossed 10 generationson a 129/SvJ background as previously described. All proceduresperformed on animals were approved by The Institutional Animal Care andUse Committees at Columbia University Medical Center.

Patient population

Blood samples from 78 patients with CHD (neonates to 18 years) andhealthy adults were collected to assess platelet reactivity and responseto cangrelor using light transmission aggregometry (LTA),collagen-coated multichannel micro fluidic devices, and geneticallymodified mice that support human but not mouse platelet-mediatedthrombosis (avatar mouse).

Patients were eligible for enrollment in the study if they were 0 to 18years of age and with known congenital heart disease. Exclusion criteriaincluded coagulation defects, known congenital or genetic conditionsexpected to affect platelet function, body weight <3 kg for pediatricpatients and <6 kg for older pediatric patients, cardiopulmonaryinstability necessitating urgent or emergent surgical/catheter-basedintervention, medications or other conditions that might significantlyaffect platelet function.

Seventy-eight pediatric patients with congenital heart disease wereenrolled in this study. Three different study population groups werechosen (Table 1).

TABLE 1 Baseline Demographic Characteristics of Cardiac PatientsBaseline Characteristics 0-28 days 1-10 years 11-18 years No. 39 31 8Mean age 12.8 4.1 15.3 Female, % patients 23.1 54.8 37.5 Ethnicity, %patients Hispanic/Latino 20.5 25.8 12.5 Race, % patients White 56.4 64.562.5 Black 7.6 6.5 12.5 Asian 15.5 3.2 12.5 Native American 0 0 0 Other20.5 25.8 12.5 Mean gestational age (weeks) 38 Diagnosis, % patientsHypoplastic left heart syndrome 23.1 19.4 0 Pulmonary atresia withintact 0 3.2 0 ventricular septum Tricuspid atresia 0 6.5 0Transposition of great arteries 33.3 12.9 0 Tetralogy of Fallot 2.6 19.425 Double-inlet left ventricle 5.1 3.2 0 Double-outlet right ventricle 03.2 12.5 Coarctation 12.8 3.2 12.5 PDA 0 12.9 0 ASD 0 0 25 Heterotaxy7.7 0 0

The first included full-term neonates (0-28 days) with a body weight of≥3 kg scheduled for cardiac surgery involving cardiopulmonary bypass. Ofthese, 56.4% were white, 7.6% were black, 15.5% were Asian, 20.5% wereof Hispanic/Latino ethnicity, and 23.1% were female. Patients withsingle ventricle pathology accounted for 23.1% of the populationenrolled in the study, with D-transposition of the great arteriesaccounting for the majority of patients (33.3%). During this period oftime, ˜23% of neonates requiring palliation with a systemic-to-pulmonaryshunt had evidence of shunt occlusion necessitating a surgicalintervention and/or rapid response ECMO. Interestingly, all eventsoccurred within 24 hours of surgery with the majority of cases prior toinitiation of aspirin therapy, FIG. 1.

The second group included pediatric patients ranging in age from 1-10years (mean of 4.1 years) scheduled to undergo left heartcatheterization for diagnostic or therapeutic purposes; the third groupincluded adolescent patients ranging in age from 11-19 years (mean of15.3 years) also undergoing left heart catheterization.

Blood Collection

For studies involving patients with congenital heart disease, blood wasobtained from a central venous catheter after clearing the line ofheparin; blood from healthy adult volunteers was obtained via routinevenipuncture. In the majority of cases, 3.8% trisodium citrate served asanticoagulant. For microfluidic studies, whole blood was collected in asyringe containing the thrombin inhibitorH-D-Phe-Pro-Arg-chloromethylketone (PPACK, Calbiochem, San Diego,Calif.) to achieve a final concentration of 100 μM. Generation of PRP orpurified platelets was performed by centrifugation as previouslydescribed.

Example 1 Platelet Aggregation Evaluation by Means of Light TransmissionAggregometry (LTA)

In this Example, platelet reactivity and response to cangrelor ofpediatric patients and healthy adults was examined.

Purified platelets were suspended to a final concentration of 400,000/μlin platelet buffer containing 145 mM NaCl, 10 mM Hepes, 0.5 mM Na2HPO4,5 mM KCl, 2 mM MgCl2, 1 mM CaCl2, 0.1% glucose, pH 7.4. Stock solutionsof cangrelor were prepared on the day of experimentation and added toplatelet suspensions (37 βC, 1,200 rpm) 10 min prior to inducingaggregation with ADP (5 μM or 20 μM ). Human fibrinogen (finalconcentration 200 μg/ml) was added to the platelet suspensions justprior to activation. Aggregation was assessed using a ChronologLumi-Aggregometer (model 540 VS, Chronolog, Havertown, Pa.) andpermitted to proceed for 6 min after the addition of agonist. Theresults are reported as maximum percent change in light transmittancefrom baseline with platelet buffer used as a reference.

Results Response of Platelets to ADP

Conflicting results exists regarding the overall reactivity of plateletsfrom neonates with cyanotic congenital heart disease as compared totheir healthy counterparts and adults, especially in response tophysiologically relevant agonists such as ADP. It was also unclearwhether platelets from this high risk population are as amenable toinhibition with antithrombotic drugs such the P2Y₁₂ receptor antagonistsas those from adults.

To address these therapeutically relevant concerns, we first evaluatedthe level of expression of the P2Y₁₂ receptor on platelets isolated fromneonates with cyanotic congenital heart disease. In comparison toplatelets from adults, no discernible difference in P2Y₂ surfaceexpression was detected (FIG. 2A); similar results were obtained for theplatelets receptors for VWF (GPIbα) and fibrinogen (αIIbβ3), which areindispensable for clot formation.

We next determine the functional response of platelets from neonates aswell as older patients with congenital heart disease to ADP stimulation.This was accomplished by calculating EC₅₀ values for the agonist usingisolated platelets in fibrinogen-supplemented buffer.

FIG. 2 (B through E) shows the mean (±SEM) percent platelet aggregationas a function of ADP concentration. Calculated EC₅₀ values were notsignificantly different for all age groups tested with mean values(±SEM) ranging from 2.9±0.1 μmol/L to 3.4±0.1 μmol/L (Table 2, P<0.001).

TABLE 2 EC₅₀ and IC₅₀ Values for ADP and Cangrelor, respectivelyPlatelets Adult 0-28 days 1-10 years 11-18 years EC₅₀ ± SEM  3.2 ± 0.2 3.4 ± 0.1  2.9 ± 0.1  3.2 ± 0.2 (μmol/L) IC₅₀ ± SEM* 0.82 ± 0.3 0.82 ±0.2 0.79 ± 0.2 0.85 ± 0.2 (nmol/L) IC₅₀ ± SEM** 0.66 ± 0.3 0.74 ± 0.30.68 ± 0.3 0.76 ± 0.2 (nmol/L) *= 20 μM ADP, **= 5 μM ADP

Effect of Cangrelor on Platelet Aggregation

Cangrelor has been shown to be a potent inhibitor of ADP-inducedplatelet aggregation in adults. To date, no information exists on itsability to effectively mitigate the ADP response of platelets fromneonates with congenital heart disease. To this end, we calculated IC₅₀values for this P2Y₁₂ receptor antagonist using low and highconcentrations of ADP (5 μM versus 20 μM). Consistent with resultsobtained by flow cytometry and in ADP-induced platelet aggregationstudies, no statistical difference was observed in the amount ofcangrelor needed to achieve half-maximal inhibition at eitherconcentration of agonist (FIG. 3A through D (20 μM ADP), FIG. 4A throughD (20 μM ADP), Figure E through H (5 μM ADP); Table 1, P<0 .001).Similarly results were observed for older populations of patients withcongenital heart disease.

Example 2 Platelet Adhesion in Flow Evaluation of Neonates with SingleVentricle Physiology using Multichannel Microfluidic Device

In this Example, the platelet adhesion of neonates with single ventriclephysiology was examined by means of multichannel micro fluidic device.

A parallel-plate flow chamber was used to assess platelet accumulationon surface-immobilized plasma VWF at a wall shear rate of 1,600_(s)-1.29, 31 In brief, a polyclonal anti-VWF antibody was absorbedovernight (4° C.) to a six-well tissue culture plate. Subsequently, theplate was washed and nonspecific interactions blocked by the addition ofTBS containing 3% BSA, pH 7.4 (30 min, 37° C.). Human or murine(VWF^(HA1)) plasma obtained from heparinized whole blood was added andthe plates placed at 37° C. for an additional hour prior to use.Citrated whole blood was then perfused over the reactive substrate for 3minutes, followed by the addition of platelet buffer lacking CaCl2 for 1min. The number of platelets attached per unit area was determined byoffline analysis (ImagePro Plus, Media Cybernetics, Bethesda, Md.) ofrecorded digital images. For GPIbα inhibition studies, mAb 6D1 (10μg/ml) was added to anticoagulated human blood for 10 min before use.

Micro fluidic devices with 8 individual channels (250 μm wide×60μm-high) were fabricated in polydimethylsiloxane (PDMS) as previouslydescribed. The device was reversibly vacuum-sealed to a glass slide withits flow channels aligned perpendicularly to a patterned type 1 collagensurface (1 mg/ml). To visualize platelet accumulation over time, anAlexa Fluor 488 conjugated, non-function blocking mouse anti-human CD61(GPIIb/IIIa) antibody was added (1:50 ratio) 7 min prior to performingexperiments (0.125 μg/ml final concentration).

Whole blood from neonates with single ventricle pathology or healthyadults was perfused over the prothrombotic surface at an initial wallshear rate of 100 s⁻¹ by withdrawal from a single outlet into a syringepump (Harvard Apparatus Pump 11 Elite, Holliston, Mass.). Plateletaccumulation was visualized (10× objective lens) using an automatedinverted microscope system (DMI6000, Leica) equipped with a CCD camera(DFC365FX, Leica). A custom stage insert held three microfluidic devicesallowing replicate testing of four conditions. Images were captured in30 s intervals for a total of 5 min. Platelet fluorescence intensities,which are directly proportional to the total platelet mass were measuredand analyzed with Image J software (Image J; NIH, Bethesda, Md.). Thecenter 65% of the prothrombotic region was selected for analysis toavoid edge effects. The initial image was taken as background andsubsequent images were background corrected. Platelet adhesion andaggregate formation was not observed upstream or downstream of thecollagen trip prior to full channel occlusion.

Calculation of half maximal inhibitor concentration and Cangrelorsensitivity Background-corrected fluorescence values were fitted with a4 parameter dose-response model.

${FI} = {A + \frac{A - B}{1 + 10^{\lbrack{({{Lo}\; g\;{IC}_{{{{50 - C})} \times D}\rbrack}}}}}}$

where C represents the Cangrelor concentration; FI, thebackground-corrected fluorescence of the corresponding region ofinterest; A and B, the minimum and maximum intensities, respectively;and D, the Hill coefficient. The data was fitted by a log (inhibitor)vs. response routine in GraphPad Prism 5.00 (GraphPad Software, LaJolla, Calif.).

Results

Further evidence supporting the in vitro potency of cangrelor inreducing the aggregation of platelets from neonates with singleventricle physiology was provided in microfluidic studies that recreatethe hemodynamic conditions of thrombosis. Whole blood collected in PPACKwas treated with various concentrations of cangrelor and then perfusedover surface-immobilized collagen. In each experiment, 8 simultaneouslyforming thrombi per device were imaged in real time. Fluorescentlylabeled platelets were observed to accumulate only at the site ofcollagen exposure, with minimal non-specific upstream or downstreamadhesion. Determination of surface fluorescence at 300 s (FI_(300s))permitted calculation of effective IC₅₀ values, which were 0.69 nM and0.95 nM for neonates with CHD versus healthy adults, respectively (FIG.4I and J).

Example 3 In Vivo Thrombus Formation Evaluation from Pediatric and OlderPatients with Congenital Heart Disease

Administration of anesthesia, insertion of venous and arterialcatheters, fluorescent labeling of human platelets, and surgicalpreparation of the cremaster muscle in 12 week old male VWF HAI micehave been previously described.

Human platelets (700K/μL) were continuously infused (25 μl/min) througha catheter placed in the ipsilateral femoral artery 2 min prior to andduring laser-induced injury to ensure a level of circulating cellsequivalent to humans.³³ Injury to the vessel wall of arterioles (40-65μm diameter) was performed with a pulsed nitrogen dye laser appliedthrough a 20× water-immersion Olympus objective. Human platelet-vesselwall interactions were visualized by fluorescence microscopy using asystem equipped with a Yokogawa CSU-22 spinning disk confocal scanner,iXON EM camera, and 488-nm laser line (Revolution XD, Andor Technology,South Windsor, Conn.) to detect Calcein-AM-labeled cells, respectively.The extent of thrombus formation was assessed for 3 min after injury andthe maximal area (μm²) of coverage determined by off-line analysis(ImagePro Plus, Media Cybernetics, Bethesda, Md.).

After establishing a baseline for normal thrombus generation in injuredarterioles, cangrelor was then given initially as an intravenously bolus(30 μg/kg) and then as a continuous infusion (4 μg/kg/min) as describedin previously clinical trials.

A minimum o f 5 mice per patient group were studied (2 and 4 arterialsegments pre and post-cangrelor per mouse, respectively).

Statistics

To compare mean thrombus areas between different treatment groups, wefit linear mixed models with random intercepts for each study animal.Linear mixed models permit comparison of mean differences betweentreatment groups while also considering the effect of the clustering ofthe data on the SEs resulting from multiple measurements obtained fromeach mouse used in intravital studies. In the case of plateletaggregation studies, values are presented as mean ±SEM. A 2-tailedStudent t test was used for comparisons between control conditions andtreatments. Differences with values of P<0.05 were consideredstatistically significant.

Results In Vivo Efficacy of Cangrelor

Previously, we have shown the preclinical utility of an avatar mousemodel that preferentially supports human and not mouse platelet-mediatedhemostasis and thrombosis.

This switch in species specificity for platelets resulted from theincorporation of the R1326H single mutation into the A1 domain of mouseVWF (VWF^(R1326H)), and more recently by replacement of the entiredomain with its human counterpart (VWFHA1).

Of note, VWF mutant animals have a profound bleeding phenotype due tothe inability of mouse platelets to stably interact with damagedvascular endothelium. As human platelet interactions with VWF is key tothe initiation of thrombus formation in this avatar mouse model, wefirst evaluated the ability of platelets from neonates with CHD toaccumulate on surface-immobilized human or murine VWF^(HA1) underarterial flow conditions. Importantly, platelets from former accumulatedon plasma VWF from humans or VWF^(HA1) mutant mice at levels comparableto those from healthy adults (FIG. 5A and B). Moreover, no significancedifference was observed in the number of platelets from neonates thatattached to either substrate (2,432±55 platelets/mm² versus 2,223±156platelets/mm², respectively; P=0.84). Importantly, this interactioncould be inhibited by the addition of the monoclonal antibody 6D1 thatblocks the ability of the platelet receptor GPIbα to interact with theA1 domain of VWF.

Although GPIbα initiates platelet deposition at arterial shear rates,this adhesive interaction is labile in nature permitting platelets totranslocate in response to forces generated by flowing blood. Ultimatelyit is the platelet integrin receptor αIIbβ3 that stabilizes adhesion byengaging with ligands such as VWF in response to ADP and/or thrombin.Consistent with this scenario is the ability of abciximab, an inhibitorof human αIIbβ3, to prevent the firm adhesion of platelets frompediatric patients with CHD or healthy adults to surface-immobilized VWFin response to ADP-induced activation in flow (FIG. 5C).

After establishing that plasma VWF^(HA1) supports attachment as well asADP-induced firm adhesion, we next set out to determine the potentialtherapeutic effect of cangrelor in preventing human platelet mediatedthrombus in vivo. The dose and route of administration of the drug wasbased on previous clinical trials in adults undergoing PCI.

Fluorescently labeled human platelets were infused continuously througha catheter inserted into the femoral artery and their behavior inresponse to laser-induced arterial injury monitored before and afteradministration of cangrelor. Consistent with the requirement for ADP topromote a second wave of aggregation, P2Y₁₂ receptor blockade onplatelets from pediatric cardiac patients yielded a ˜45% reduction inthrombus size (P<0.0001) (FIG. 6 A through F; see Table III).

TABLE III Linear mixed model comparing average human platelet thrombussize (μm2) in VWFHA1 mutant mice. The contrast column is the meandifference between thrombus size pre- and post- administration ofcangrelor for each age group tested. Standard errors and statistics wereobtained from fitting of the linear mixed model. Age Contrast Standardgroup estimate error P-value 0-28 days 2,261 224 <0.0001 1-10 years3,314 224 <0.0001 11-18 years 3,475 224 <0.0001 Adult 3,501 224 <0.0001

By contrast, administration of abciximab abrogated platelet accumulationby >90% (P<0.0001). Similar results were obtained using platelets fromolder patients with congenital heart disease and healthy adults.

Various changes could be made in the above methods without departingfrom the scope of the invention as defined in the claims below. It isintended that all matter contained in the above description, and asshown in the accompanying figures, shall be interpreted as illustrativeand not as limiting.

1. A method of treating or preventing shunt thrombosis in a patientcomprising administering a pharmaceutical composition comprisingcangrelor to the patient wherein the patient is suffering fromcongenital heart diseases.
 2. The method of claim 1 wherein the patientis undergoing shunt surgery.
 3. The method of claim 2 wherein the shuntsurgery is selected from the group consisting of systemic-to-pulmonaryartery shunt, Blalock-Taussing shunt, central shunt, and right ventricleto pulmonary artery palliative shunts.
 4. The method of claim 3 whereinthe shunt surgery is systemic-to-pulmonary artery shunt surgery. 5.(canceled)
 6. The method of claim 1 wherein the patient is undergoingshunt surgery or stent implantation.
 7. The method of claim 6 whereinthe shunt surgery or stent implantation is selected from the groupconsisting of systemic-to-pulmonary artery shunt, Blalock-Taussingshunt, central shunt, right ventricle to pulmonary artery palliativeshunt, and ductus arterious stent.
 8. The method of claim 7 wherein thepatients suffer single ventricle physiology palliated withsystemic-to-pulmonary artery shunt.
 9. The method of claims 1 whereinthe administration is intravenous.
 10. The method of claim 1 wherein theintravenous administration is a continuous infusion.
 11. The method ofclaim 10 wherein the amount of cangrelor administered is between about0.1 and about 4 μg/kg/min.
 12. The method of claim 11 wherein the amountof cangrelor administered is between about 0.1 μg/kg/min and about 1.5μg/kg/min.
 13. The method of claim 12, wherein the point in time whenthe pharmaceutical composition is administered is between about half anhour and about 24 hours from the termination of the shunt surgery orstent implantation.
 14. The method of claim 13, wherein the point intime when the pharmaceutical composition is administered is betweenabout 2 and about 4 hours from the termination of the shunt surgery orstent implantation.
 15. A method for preventing and/or treatment ofshunt or stent thrombosis comprising: i) performing the shunt surgery orstent implantation; and ii) administering a composition comprisingcangrelor after the surgery.
 16. The method according to claim 15wherein the composition is administered as a bolus, or as a continuousinfusion, or as a bolus followed by a continuous infusion, or as acontinuous infusion followed by a bolus.
 17. The method according toclaim 15 wherein the composition is administered as a continuousinfusion for at least about 10 minutes to about 72 hours or untiladministration of an oral agent for prevention of platelet aggregation.18. The method according to claim 17 wherein the composition isadministered as a continuous infusion for at least about 10 minutes toabout 2 hours.
 19. A method of treatment of a patient comprisingadministering a pharmaceutical composition comprising cangrelor to thepatient wherein the patient is undergoing shunt surgery or shuntimplantation and then administering oral antiplatelet therapies to thepatient.
 20. The method of claim 19 wherein the shunt surgery or stentimplantation is selected from the group consisting ofsystemic-to-pulmonary artery shunt, Blalock-Taussing shunt, centralshunt, right ventricle to pulmonary artery palliative shunt, and ductusarterious stent.
 21. The method of claim 20 wherein the administrationfurther comprising: i) the administering a continuous infusion ofcangrelor after shunt surgery or stent implantation for at least onehour or longer; ii) discontinuing the treatment with cangrelor; and iii)administering the oral antiplatelet therapy.
 22. The method of claim 21wherein the continuous infusion of cangrelor is at dosage between about0.1 and about 4 μg/kg/min.
 23. The method of claim 22 wherein thecontinuous infusion is between about 0.1 and about 1.5 μg/kg/min. 24.The method of claim 22 wherein the continuous infusion is between about0.1 and about 1 μg/kg/min.
 25. The method of claim 22 wherein thecontinuous infusion is between about 0.1 and about 0.5 μg/kg/min. 26.The method of claim 22 wherein the continuous infusion is between about0.1 and about 0.3 μg/kg/min.
 27. (canceled)